The present invention relates to a mount and support to be used in and being a part of a rolling mill for rolling hollows including a rotating internal tool; further having a tool rod which bears against the mount to take up the reaction force of rolling operating in axial fashion. The support and mount being a thrust mount is of carriage-like construction to be movable for purposes of tool and rod change; furthermore, the tool rod is (a) supported transversely to the axis of rolling and (b) caused to rotate about its longitudinal axis.
Rolling mills of the type to which the invention pertains are in the foregoing broadly characterized. This is realized, for example, in rolling mills with oblique and inclined roll axes being provided for piercing billets or for stretching or widening existing hollows. The internal tool referred to above is in these cases a mandrel which is held on a rod between the rolls. Even if the mandrel is rotatably mounted on the mandrel rod there is a significant wear whenever the mandrel it has to be set into rotation inside the rolled stock.
European Pat. No. 41 464 suggests to couple the mandrel rod at its rear, free end mechanically with a rotational drive so that during rolling a synchronization obtains as between the rotation of the rolled stock and of the mandrel. However, this arrangement is disadvantaged by the fact that the mechanical wear of the mandrel is now in effect shifted over to a stop and to the end of the tool holder i.e. the mandrel. This in turn interferes with the exactitude that is necessary for maintaining the axial position relative to the rolls as this position has to be maintained for adequacy of the rolling process. Also, this known approach is disadvantaged in that the mandrel position depends now exclusively on the cooperation of planar support surfaces of the stop with the reaction of the rolls themselves. Axially retracting the mandrel from the stand is possible only if one has, in fact, sufficiently high reaction forces of rolling.